Suppose that a robot is placed on the Cartesian plane. At each step, it is…

Suppose that a robot is placed on the Cartesian plane. At each step, it is allowed to move either one unit up or one unit right. That is, if the robot is at position (i, j), then it can move to either (i + 1, j) or (i, j + 1).

How many distinct paths are there for the robot to reach the point (10, 10) starting from the initial position (0, 0)?